Traffic actuated control system



July l5, 1941.

H. A. w|| cox mj AL TRAFFIC AGTUATED CONTROL SYSTEM 2 Sheets-Sheet 2 Filed July 2 0, 1940 INVENTORS com/va .Jb/,w l. 4p/rie' ATTORN EY www Patented July 15, 1941 TRAFFIC ACTUATED CONTROL SYSTEM Harry A. Wilcox and John L. Barker, Norwalk,

Conn., assignors to Automatic Signal Corporation, East Norwalk, Conn., a corporation of Delaware Applioation July zo, 1940, sorial No. 346.517

16 Claims.

This application relates to traic actuated tramo control systems and especially to systems of this kind for installation at a constricted section of roadway capable of permitting traflic flow only in one direction at a time, or at particularly wide road intersections or the like, where a relatively long time is required to clear one trac flow beyond the point of possible conct with another. Such a system is of use in all locations where there is a relatively long or extensive controlled area and it is desirable to clear this area of one traffic flow before right of way is accorded to a conflicting traflic flow, and to so accomplish this without imposing unnecessary delay to the conicting traffic flow.

In accordance with the invention a traliic Acontrol system of this character is provided in which the right of Way is accorded to either approach tothe relatively long Zone of interference in response to trac actuation on such approach, but before such accord of right of way to the first approach the right of way is interrupted on the other approach and right of way is maintained ticular value at a long narrow bridge or tunnel or a relatively narrow section of curved roadway where it is unsafe or impossible to permit tralc to pass in two directions for example.

Traffic actuated trafficvcontrol systemshave in the past been built for numerous types of in` stallation and for many varied conditions of operation. For example systems of thejtrafic tuations of trafc detectors inthe lanes of .flow

are well-known. Long in use also are systems c whichprovide that a Vunit of tramo which actuates a detector during a'change'of right of way,

or amber signal, period procures for itself extension of the change period beyond the normal duration ofthe period for safe passagegof the i actuatingtrafc unit through the intersection interrupted on the first approach for sufcient.v

time to clear from the zone of interference any traic which may have entered from such other approach, and reduction of this period of interruption of right of way to both approaches is provided in accordance with the amount of time vwhich may have elapsed after the last moving vehicle entered from the lirst approach Vbefore the arrival of the first vehicle on the other ap'-v proach.

The system preferably provides for the right of way to remain on the approach on which traffic has last arrived in absence .of any trafilc on the.

rival of eachI vehicle with Ithe prolongation of right of way by such vehicle on one: approach,

and becomes an actual right of way interruption clearance period only in event of arrival of va vehicleV on the otherV approach andthen onlyfor the balance of such overall time remaining afterk arrival of the latter vehicle.V

The system of the present lnvention'llasp para before right of way is accorded to the opposing y traffic ow.

The present system, however, is adapted par` ticularly for controlling vfor example traffic mov; ing along a roadway having a constricted section l of considerable length as caused for instance.,`

by thepresence ofa narrow bridge through or l over whichtraffic may safely be permittedto flow Trafc control I' signals mounted at the ends of the oonstrictedn area are governed by a controller under the inf-v"v fluence of traflic detectors set inthe approachesV to the constricted section, and inthe absence of J` other trac a single vehicle actuating a detector immediately receives accord of'right of'way fol-` lowing the usual brief amber` change period,jif o the control is not already showing right, ofway,

in only one direction at a time.

for the lvehicle as a result oiV prior traflic` actu.-`

ation on the same approach. "Succeeding ve-Y c hicles entering the restricted section are eachvassured a minimum time period for clearing thearea expired. Y v a there should be no arriving vehicles on the said opposite approach until the minimum clearance period for the last vehicle to enter the area VfromV i the rst approach has expired, there will be noperiod in 'which right of way is denied to bothV approaches and accord of right of way will be transferred directly, following the usual brief ance interval as described, right of way will be accorded thereafter to the waiting vehicle. In this event the controller will automatically retransfer right of way for permitting resumption of passage of the continuous flow which hadbeen cut off. Each transfer of right of wayffrom one approach to the other always establishes accord of right of way for at least a vminimum period which is capable of being prolongedby additional vehicle actuation on the lane having right of. way within the right of way period.

Itwill be appreciated', therefore that each: vehicle entering-the restricted section during the right-of way periodfor such vehicle by the present system is assured of'safe travel time period in which to pass through the area, and thatk traffic approaching the. area will underv no conditions be delayed.- whenthejareal is free of traii'ic, yand that under all; conditions of -arriving traffic the controller will governV movement through` the area expeditiously, safely and y eiiciently.

Itlistan object of the invention, therefore,. to provide a traiic actuated traic controll system for. constr'icted.k roadway` sections, Wide intersections-'andthe likev which shalltransfer. andaccord. right of Way to interfering flows of traffic for-,varying time periodszin accordance with trafiic detector. actuations l and which. shall provide a minimum-clearance time period for every vehicle entering the controlled area before the completion of which period right of way. cannot be accorded to aconflicting traffic flow.

Itsis 'a' further object that a systeml ofv thischaracterbe provided which-shall deny right of Wayf on all approaches. to the controlled area during-any portion of the minimum clearance periodwhich remains. after detector actuation onan'approach not having right of-way before transferringaccord of right of way to the approach4 ofthe actuation, thus safeguarding the completingV oflpassage of ,any vehicle proceeding through .the area-and-without causing delay to thevehicleon the approach not having right of Wayifrnot required, by the actual presence of trac. inA thev area.

Itisfa further object of the invention to provide an,improyed traiiic right of Uway control systemlfor interferingtraiiic lanes having a relatively longzone of. interference so. asto require a relatively long time for the last vehicle enteringithiszone. from one lane during the right of wayperiod. of` that` lane. tov clear, through this zonecof interference before right of way can safelyybe accordedtothe other lane, and in which a clearance-periodis provided in which right of-,Wayris interrupted to-both of the interfering lanes-concurrently for sufficient time to clear the last,Vehicle-entering on a right of way signal fromY onerapproachbefore right ofA wayis accorded-totheopposite approach. i

Agnother objectisto-provide a traic control systemfhavinga relatively longclearance period i of .interruption of right of way normally appearinguponrtransfer of` right of way from traiiic on-yone approach to-traflic onl another, interfering traiiic approach, and in which the time length of this right of way interruption clearance period is automatically reduced in accordance with the amount of time the right of way has remained on one approach since arrival of the last vehicle on that approach, so as not to delay unnecessarily a vehicle arriving on such other approach'at aV time when no vehicles are arriving-or have recently arrived on the iirst approach which has had the right of way.

It is an object of this invention to provide a traiific control system for interfering traino lanes in which the Zone of interference between the two lanes is relatively long, in which right of way kis accorded' alternately to the two lanes respectively in responseto trailic arriving in the respective lanes, said system including the provision of a period ofr interruption of right of way in both lanes after termination of accord of right of way in one ofjthe lanes and before accord of right of way to the other lane in response to traiic in the latteri'lane, with the period of interruption of right of way to both lanes having an ultimate length suflicient to permit a vehicle to clear through the Whole zone of ,interference but having this period reduced from such ultimate length in accordance with the amount of time which may haveelapsed from the arrival of the last vehicleA on'the approachhaving right of way be- Y fore the arrival of the rst'vehicle on the other lane while'right of way'is interrupted therein.

It' is an object ofthe invention to provide a traino control system for the accord of right of way alternately to twojapprcachesl to a relatively long zone of interference in which a short period of extension ofv right of way is provided following the arrival of each vehicle on the approach having right of way and in which an overallclearance time period is provided following the arrival of each such vehicle and of considerablyA greater length than the right of way extensiontime period, and in which rightof way'is interrupted in the first approach, in response to expiration of the right of way extensionperiod upon or after the arrival of the first vehicle on the second approach, with the time length of such interruption of right of way to botliv approaches representing the difference between th'e, overall clearance period and the extension period.

Itis an yobject of the invention to provide a traffic .control system for interfering traiic lanes in which :there is a relatively long zone of interference between the lanes for traffic to clear and inwhichthe right of way is accorded alternately tothelanes respectively, said system providing a short period timer. for prolongation of right of way for abrief period from arrival of each veh-iclein the lane having right of way and at the end of which brief period the right of way on the rst lane will be interrupted in response to traffic arriving on the second lane, and providing a second timer to time a longer time period than the rst from arrival -of each vehicle having the right of way, with this longer time suflicient to permit ofl the second Itimer but only of suliicient length to clear t'he last vehicle arriving with the right of Way,v whereby any vehicle arriving on a lanenot having right of way while right of way is on the-other lane will obtain transfer of rightof way substantially immediately to its lane, if no car has '-'arrived on the right of way lane for a prior period exceeding the clearance time.

It is an object of the invention to provide a traflic signal system for interfering traflic lanes in which there is a relatively long zone of interference for .trai-lic from one lane to vclear so as not to interfere with ltraiic entering from the'other lane, yand in which the usual green, yellow and red traic signals are provided with the green signal displayed to only one lane at a time while the red signal i-s displayed to the other and with the yellow signal displayed after t'he green and before the red to give a brief period of warning to moving'traic that is about to be stopped, 'and in which an overall clearance period is timed from the arrival of each -car on the lane having the right of way to delay transfer Vof the green signal to the other lane for su'icient time to permit such vehicle on -the first lane to clear the zone of interference and a shorter period 'is also timed for prolongation of the green signal from the larrival of such vehicle arriving on the first lane for the green signal to be changed to yellow on the first approach substantially immediately in response to a vehicle on the other approach upon entry of the vehicleon the first approach into the zone of interference if thereare no immediately follo-wing vehicles on .this lapproach, and

for the yellow signal to be displayed for a very brief period vafter which .the red signal will be displayed to the rst approach as well'as maintained in the second approach for the balance of the overall clearance time.

The nature of the invention will be clear ,from Y the following description of one embodiment to- Y gether with the accompanyingI figures lof the drawings, in which: l

Figures 1 and 2 together comprise a circuit diagram of 'an embodiment of a controller a`c' cording to the invention, and right of way signals and traflicdetectors for governing movement of traffic in one direction at a time throughl a conpasses across a narrow bridge for example.

The roadway shown is adapted generallytoV stricted section of roadway, where the roadway;

stricted by its passage through a bridgeV BR where the narrowed roadway can safely Vcarry only a single lane of traic. As represented in the draw` ings by the section or break at the center part of the bridge the narrow constricted section may be of considerable length. Theusual green, amber,

and red signal indications may be presented by the signals G'A,` AA. l and RA for traflic onap-Y proach A' from which traic enters the restricted section from the left toward the right side of the Figure l, and by the signals GB, AB, and

RB for Ytrailic on approach B from which traffic enters vthe bridge area from the right toward the left side of the drawings. Traflic actuatable devices or detectors DI, D2 which may be Yof, the

pressure-sensitive type or magnetic type or other suitable type ladapted to operate on electric circuit when actuatedby a vehicle are located'inv the approaches to the restricted area' preferably some -distance in advance of the signals. In -the as switches :adapted to be lclosed by actuation. K

' Ihe control apparatus for the signals lis oon-1 veniently mountednear one set of.' signals and connected to the signals and to the detectors as indicated in the drawings. i v

-It will beappreciated thatfthe traiiic -control system disclosed may be used advantageously in many types of installations besides the one-way restricted traffic area shown. For example it may be used yat intersections of two particularly wi-de roads.r It isadvantageous for use'at other types of intersections', such as the crossing of a road of normal Ywidth with a'particularly broa-d road, or'wide crossings of more than two roadways, or in fact wherever it is desired that an assured clearance period of considerable duration for the last vehicle entering the controlled area be pro-A PBare open and ARS and BRSare closed as shown in Fig. 1. It will also be assumed for purposes of illustration that the distance vfrom either detector DI or D2 through the restrict-ed Iarea or interferencezone acrossthe bridge BR is about 600 feet, an-d that .the low range of speed through this Zone is '40 feet per seconder about 27 miles per hour. I't will-be understood that these gures are merely illustrative and that the actual figures may be considerably lower -or much Vhigher at various locations .to which this. system may be,

applied. Under these conditions the vehicle will require 15 seconds to clear' from Athe detector through the entire interference zone.

Inthe condition of absence of traffic on both approaches and in thezone of interference the right of way` will rremain on the approach onV which the last previous vehicle arrived yand cleared through thezone o f interference. Assum-v ing that'the last previous vehicle arrived on approach A then theright of way'A will remain on approach A with the green signal displayed there andthe red signal displayed to approach B. These signals will remain continuously displayed in this fashion inr absence of any traffic on approach B whether or not there is any trafc von approa'chAl V y In case' a vehicle should arrive on approach B whil-e right of way ison approach A but in the absence fof traflic on' approach A for an appreciabletime such as 15 seconds for example prior to thearrival of such vehicle on approach B, the red signal on approach yB will remain Vdisplayed asbefore but the 'green signal on approach A will be extinguished and the "amber signal on approach B but this signal is now substantiallyVV immediately extinguished vandthe green signalv on Vapproach B displayed. i The .green signal remains displayed on approach B with'th-e red sig? nal on approach Afora Vminimum time period controlled by a timing device and; this signal dise play thereafter lcontinues -inr 'absence of arrival of any traflic onapproach A. H

Assuming thejoriginal signal display again with V rightof way on approachiiA-,and considering the case of the arrival of a-avehiclefion approach Bf immediatelyl afterarrival-of avehicle on approachy A',V the. signal display will remain unchanged:with theright ofz Way maintained` on approach Av fora shorttime .period from lthe arrival ofthe vehicle on1A. Theirght of Way is thus Aextended on'A for this short time-'period for the protection-of this vehicle on A; Inabsence of furthervehiclesnarrivinggon-1A thergreen signal on A willv be extinguished 'at the end; of this short extension time-period andthe amber sigf nal will be displayedon A wh'ilethe4 red signal remains onv Bfas before.r After aybrief amber period asv` before, the amber signal willbe extinguished and the red signal displayed on-approach A. Normally'the short rightof Wayfextension period and the following amber'period willconsume only a few seconds andassuming` a total overall-clearance period of seconds Vthe red signal maintained'on approach0 B -in addition to the red signal on approach A- fora further time period 'representing the remainder of v`theoverall clearance period, as measured by atiming device. After this clearanceperiodfhas beenn completed the-red signal-is extinguished on Bfandv the green signal is displayed there for at least a minimum period as before described.'

Returning to the original signal display againy with rig-ht of .f way.- on approach A" and considering the case offarrival'of avehicle-.on` B at a time ora-.continuous fsuccession of closely Vspaced Yvehiclesearriving lon -approach-A, a-'maximum time limit Will become effective as a result -of arrival of the-vehicle-on- B so` that rightof way cannot be maintainedY beyond such maximumtime limit. As eachl of .the-succession of vehicles onapproach AV actuatedetector DI within-suchmaximumV limit the. right ofwayfwill ybe Vprolonged'on approach A for the short extension period',- and assuming that the vehicles are soV closely `'spaced thatr each vehicle` arrives withinfthecshort-exten;- sion period Aprovided by the vehicle preceding it,

the rightofwaywill be maintained von approach A upto the` maximum limit; and fatthis 'limit the greensignalV on A'4 will be extinguished 'and thev amber' signal'displayed for a short period as before4 described, afterwhich the -amberV signal vwill beextinguished on A- and Athe red-signalxdisplayedf there. The-operationofthe maximumV limit in terminating rightn of way on'AA- will' ordinarily occur within a moment of actuationofl detector DI by a vehicle on A and thus substantially the full overall clearancetimeisv requiredforsuch vehiclefor-for the v-last vehicle enteringfro'm approachfAsc that-thered signal is maintained on approach vB as well asonapproachv A after the amber period for Aforsubstantially a full clearance period -after which thegreen signalis substituted forthe -redsignalon- B as `previously 'de` scribed, but inthis case the righ'tof Waywill be returned *to approach-A at'the-'end'of the minimum period on B; in absenceof-further vehicles on B, so asltol care for the-traffic onA interrupted" by the maximum.' Ifl further vehicles arrive on B to prolong the right of-way'on B `the right'ofv wayV willI be` returned `to` A' afterthe'proper B' clearance periodat-the end of either'. the BM' right of Way'extension period or B maximum periodv depending upon how long vehicles continue to arrive on B. i y

With switches ARS' 'and BRS'both closed asV assumed, the system is-symmetrical with' respect tothe two approaches A-and B andv therefore the transfer.' of y'right ofiway fromapproachB to. ape-' proach A Wi'llltake place in the same fashion for various traflic .conditions as previouslydescribedf for transfer of rightofway from.A.to- B-under 5 such traffic conditions. but withthese conditions.

reversed-as to thetwo approaches.

The several features of operation just describedv with respect to various traic conditions are providedin accordance with the present preferred l0 embodiment of the invention by the provision of a minimumright of way timer device, a right! of Way extension timer device having a relatively short time period, a maximum right of way timer device "having a relatively long time period, and

period. This.` clearance time period is ordinarily of shorter ylength than the maximum time period .for zones of interference of'ordinary length al' though it would be possible under conditions of an extremely long zone l(if-interference and relatively light traffic that itV might be desirable to have the maximum time' period shorter than the :overallclearance time period'. A timerv device is- Y alsoprovidedfor'the amber period. Ihe right of` Way extension period timer and the overall clearanceperiod: timer are each reset to restart theirftiming period`responsive to each traffic mactuationA by vehicles arriving with the right of way and in the present preferred embodiment theseY timers aren reset at the moment ofactuation and measure their time period from that moment, butitwill be appreciatedV that similar but somewhat inferior results may beobtainedby the use of a recycling type of atimer which Will'be actuated in 4each successive4 extension time period to. add.; another timeA period' after completion of' i the current time period. 40Lv Referring now to the drawings for a more detailed Yconsideration of the present embodiment of the-invention they trafiic'signal controller represented therein comprisesa number of setsof contacts for controllingwthe right of way signals Iiizandcircuitsfor-timing the display periods ofthe signals, these contacts beingoperated by a cam shaft whichis-moved step-by-step through a cycle by means ofa solenoid' and ratcheting mechanism.- The stepping of the solenoidis govierned by atiming circuit employing a gaseousl discharge tube-condensertimerfarranged to have its timeperiodsvaried undervcontrol ofthe vehi'- cle .detectorsflocatedin the approaches to the restricted. area. Under a number of circumizstancesmore than one time period isfsimultaneously timed' and the'present controller. utilizes a plurality oftiming circuits forthis purpose. The controlleris arranged to operate from-an alternating current supply I, 2.- 'Io providev dimi; rect current for the timing circuits a transformer- 3 supplies rectifier 4. The ungrounded AC lead 211s denoted by a plus -in a circle and the ungrounded. DC lead` Sis denoted by a plus in-a square. 'Ihe' lcommon grounded AC and DC G51-lead. is represented-by a minus in a circle andl square. yCamfoperated contacts are shown alignednear, the rightof the drawings and' thepositions of the cam shaft in which each contact pair. is closed in the sixpositioncycle areindi- Tfacated in the chart at. the extreme. right of` the drawings.

In describing operation o f thesystem it will beV assumedy first of all vthatthe cam shaft is in p osition 6 the Arappr'oach right of.way period andv 7v that'there is no traffic on either approach. It

tact C9 and contact W3 of deenergized relay RRV to AC minus lead l. Under the condition of no traic assumed, a charging circut for condenser QJ is completed from DC plus lead via highr resistance VA, cam contact C5 leadY lcondenser QJ, resistance ZJ vto minus lead- I. Condenser QJ ,over -a time period proportional to the amount of control resistance VA in circuit, is charged to a voltage in excess of that required to cause discharge through the gaseous discharge tube FJ, butas the circuit through the tube FJ paralleling the condenser QJ Via lead I4, relay contact T19, lead I5, relay contact K3, tube FJ, relay J, lead I6, relay contact bd3, cam contact C28, lead I1 to AC minus lead I, is open at contact bd3 in the absence of detector actuation, no discharge through the tube FJ can occur at this'time.'

If now a vehicle arrives on approach B actuating detector D2, relay BD is energized by a circuit from plus lead 2 via lead II, relay coil BD and detector D2 to minus lead I, and relay'BD is locked-'in over contact bd I, lead I2, cam con-l tact CIB, lead I3 to minus lead I. Operation of the relay BD enables the circuit previously traced parallelling condenser QJ to be completed via contact bd3. denser QJ now exceeds the flash potentialof tube FJ as result of completion of its charging period as previously described, the circuit through the -tube becomes conducting and relay J is momentarily energized by the discharge of condenser QJ through it and a circuit is completed from minus lead I via relay contact 9'2, cam contact C6, lead I8, through solenoid S to plus lead 2, energizing solenoid S. The momentary energization and deenergization of solenoid S advances the cam shaft one step to position I.

In position I the A approach green light GA is extinguished by breaking of cam contact C9 and the A approach amber, or right of way change signal, AA is displayed by closure of cam contacts CI Il. The duration of the period is timed by the charging of condenser QK from DC plus lead 5" In addition to causing operation of the sole-v noid the momentary energization of relay K completes a circuit at contact lcI- for energizing relay RR over cam contact Cil, lead 20, closed switchV ARS. v

The advancement o the cam shaft to position'- 2 causes extinguishing of the A yapproach ambersignal AA by opening cam contacts CI Il, and en'- ergization of the A red signal RA by closure of camcontacts CI I in position 2. B red signal RBl is maintained energized despite the opening of Since the voltage across con-l cam contacts C22 by circuitithroughcam con-` tacts C20 and closed contact 112. Thus the normalr signal indications for cam shaft position 2 are superseded for the moment by stop signals to both approaches. However under the traic conditions here assumed of no traic'having entered the restricted area from the A approach for a considerable time period the denial of'right of way to both lanes is immediately ended by deenergization of relay RR as explained below. The al1-red period under this condition of immediate deenergization of relay RR is of substantially no duration whatever, being of the order of a fraction of a' second, and the normal signal indications for cam shaft position 2 are then initiated, i. e., A approach red signal RA is then energized over cam contacts CI I and B approach green signal GB is then energized via cam contacts C20 and back contact Trl.

The energization of relay RR upon the terminating of the A amber signal period in position I occurs when the amber period timing ends the period by operation of relay K which at contact lcI completes circuit'to energize relay RR from. plus lead 2, relay RR, contact kl, cam contacts C4 (closed in position I), lead 20 and closed switch ARS as previously described. Relay RR is locked-in over contact W5, contact :i I to minus lead I.Y The subsequent deenergization of relay RR to terminate the all-red display in position 2 is dependent upon the timing circuit involving condenser QL which is charged gradually during preceding cam shaft positions 6 and I. This charging circuit extends from DC plus lead 5 over resistance RRA, cam contacts CI, lead 2l, condenser QLto minus lead I. Also, in positionsV 6 and I, a resetting circuit for this condenser isV Operation of relay RR as the cam shaft is Iad-` vanced to position 2 completes an operating circuit for the condenser QL via lead 2 I contact W8, lead I5, contact k3, tube FJ, relay J, lead I6, contact bd3, cam contacts C28, :and lead I1 `to minus lead I, and since there has been no resetting ofl condenser QL by vehicles the charge on condenser QL has exceeded the ilash voltage of tube FJ and relay J operates to cause immediate deenergization of relay RR by breaking the holding circuit of the latter at relay contact y'l.

' It will be apparent that in the'event ofV a ve-'` hicle fromA approach having entered the restricted area during the A approach right of way period in position 6 or during the following brief amber signal period in position I, condenser QL would have been reset and could not therefore attain the 'ftash voltage of tube'FJ for the time period required to recharge condenser QL,'which' time period isset for an overall clearance period of suiiicient length to clear the last entering vehicle through the whole restricted areal If it isV assumed as-before that a vehicle will require 15 seconds to clear from the detector through the entire restricted area for this particular location,

the resistance RRA or RRB for the A and B approaches respectively, or for both approaches if the conditions were the same in opposite directions as t required clearance time for tralc, wouldI be adjusted to provide for charging condenser QL to the ash voltage of tube FJ in seconds and thus provide :an overall clearance period of 15 seconds. e

Accordingly if a vehicle entered from A approach during the A right of way period in the cam shaft position 6, for example, the condenser QL would be reset to restart its timing of this 15 secondYK overall clearance period at the moment that'this vehicle crossed the A detector DI. In absence of further vehicles on A appro-ach for the moment the A right of Way period would be ter-l minated after a few seconds by completion of the timing of condenser QJ in position 6 and the amber signal period in the following position I would be terminated by completion of timing by condenser QK after a brief period of 1 to 3 seconds for example. This would leave a balance of several seconds of the overall clearance period to be timed by condenser QL in position 2 While red signals are displayed to both A and B approaches as a result of the energization of relay RR at the end of the amber period in position I. Accordingly the red signals on both approaches would continue to be displayed in position 2 for the balance of this overall clearance period, until condenser QL attains the flash potential of tube FJ and operates relay J to instantly deenergize relay RR which in turn at its contact 112 will extinguish the B red signal RB and at its Contact rrl will light the B green signal GB.

It will also be apparent that if a vehicle arrived at the detector DI in the A approach just a little too far behind the preceding vehicle to continue to hold the right of way on the A approach against a Vehicle waiting on the B approach for example, condenser QJ would have completed its timing in position 6 and the cam shaft would have been shifted ahead to position I and this particular vehicle would cross detector DI on A approach during the A amber period.r The reset circuit for condenserA QL controlled by the A detector DI at its relay contacts cd2 is still effective in position I since cam contacts CI and relay contacts rr'l remain closed, and thus this particular Vehicleresets condenser QL again in position I and the overall clearance period is timed from position I on, thus giving an all red clearance period in position 2 of substantially the whole length of the overall clearance before deenergization of relay RR as previously described.

The deenergization of relay RR. causes no movement of the cam shaft but extinguishes the B approach red signal RB and energizes the B approach green signal GB as previously Clescribed.

The initial B approach green period is now timed by condenser QK from DC plus lead 5 over resistance 1B, cam contacts CI3, lead 2'4, contactv rrl, which has closed upon deenergizationA of relay RR, and leadg` 25, 26 through condenser QK. When Vthe charge on condenser QK has attained the flash potential of tube FK, the latter becomes conducting and operates Vrelay K in parallel with the condenser QK, and at contact kd the operating circuit for the ,solenoid S .is

momentarily completed, all as' previously decharged over resistance VB, cam contacts-CIG, leads I0, I4. Moreover relay BD is deenergized by the opening of its locking circuit at camcontacts CI8, and by the closure of cam contacts C25 -a circuit for shunting or resetting condenser QJ upon further B approach detectoractuations is yprepared extendingvia lead I'I, through cam Contact C25, lead 21, contact bd4--when closedand lead 29, and low resistance ZY. Itv will be noted( that since the lock-in circuit for relay BD is open in this period at cam contact CI8 relay BD is only operated in this period momentarily while a vehicle is actually traversing the detector and that theresetting of the condenser'QJ and resulting extension ofv the timed period is dependent on the speed ofthe vehicle, being greater for a slow moving vehicle than for a fast one. The degree to which the extension is variableA by. vehicle speed is controlled by selection ofthe value of resistance ZY in relation to the capacity ofl condenser QJ and the time length of the momentary-vehicle actuation, according to the well known condenser-resistance-time discharge characteristic.

If there is no further trailic on the B approach relay BD will remain deenergized and contact bd4 will remain open so that condenser QJ will charge Without being reset. However until relay AD is operated by a vehicle traversing the A approachdetector DI no operating circuit parallelling the condenser QJ through tube FJ and relay J will be completed for operation of relay J and consequent operation of the solenoid by the latter. This operating circuit for relay J extends from the condenser QJ, lead I4, contact rr9, lead I5, contact k3, tube FJ, relay J, lead 28, contact ad3, lead 21, and cam contacts C25 to minus lead I.

Vehicle actuation of anV A approach, detector energizing relay AD, in addition to completing the above described operating circuit for relayr J, will also initiate operationA of a maximum timing circuit involving condenser QK. This latter circuit ensures that in; the event of further vehicles thereafter successively arriving on the B approach and resetting condenser QJ by momentary closures of contact bd4 via resistance ZY in the manner outlined above, the waiting vehicle on A approach will not be delayed for greater than a preset maximum time. The maximum timing circuit for charging condenser QK extends over high resistance MB, cam contacts C26, contact ad5, lead I9, and condenser QK, and the resistanceZK to minus lead I, and is initiated e by closure of` contact ad5. If the spacing of B approach vehicles is suiliciently close to maintain condenser QJ below the ash voltage of tube FJ until condenser QK reaches the flash voltage oftube FK, the latter will operate relay K to effect advancement of the cam shaft into position 4, the B approach amber or right of Way change period.

Whenever the cam shaft is advanced from position 3 by action of the maximum timing circuit relay K, thereby interrupting a stream of vehicles on the B approach, provision is made to ensure that without further operation of the B approach .detector right of Way will'be returned to the B approach. This circuit extends from minus lead I over contact k2 and cam contacts C21, energizing relay BD at the end of position 3 ;v a lock-in circuit for relay BD being establishedvover solenoid contact SI and relay contact .bdI while the solenoid advances the` cam shaft toposition 4, where the lock-in circuit theny extends over cam contacts CI8 and contact bdI.

Movement of the camshaft Vthrough the remaining positions 4, 5, 6 comprising the B amber period, and A approach right of way periods respectively, is similar to that described for positions I, 2 and 3. In position 4 the B approach amber signal AB is energized over cam contacts C2i and the A approach red signal RA over cam contacts CI I. Condenser QK is charged over resistance LB, cam contacts CI4, back contact bd, lead 26 to condenser QK. If right of way is being forcibly removed from the B approach thus intercepting a stream of traffic an extended amber period is provided by the inclusion of resistance ZB in the charging circuit since contact bd would be open in this circumstance. Similar provision is made in the A approach amber period at contact adfo and resistance ZA.

As the cam shaft is advanced into position at the end of the B amber periodfrelay RR is energized via closed switch BRS, cam contacts CI5, contact kl. At contact 114 the A approach red signal RA is maintained and at cam contacts C22 the B approach red signal RB is energized. Condenser QL is under charge in periods 3, 4 and 5 via resistance RRB, and cam contacts CI2 and is subject to reset in periods 3 and 4 by B approach traiiic entering the restricted area over contacts 116, bd2, low resistance ZRB. In position 5 as soon as condenser QL attains the flash voltage of the tube FJ which is connected in parallel with the condenser in position 5 by contacts 1'18 which are then closed, the all-red period is terminated as relay RR is deenergized at il; and at contacts 173, W4 the A green signal GA is energized in place of the red signal RA. The A cam shaft is not advanced. Y

The A approach initial green period is no timed by the charging of condenser QK over resistance IA. Cam contacts C2, lead 24, contact MID, leads 25, 26, and is concluded by operation of relay K which at lc4 energizesV solenoid S to cause movement of the cam shaft to position 6, the A approach vehicle interval period, where there is no change in the signals.

The resettable or vehicle interval is timed in position 6 by charging condenser QJ over resistance VA, cam contacts C5, subject to resetting by A approach vehicles crossing detector DI and momentarily shunting QJ by low resistance ZY at contact ad4. B approach detector actuation initiates the maximum timer circuit of condenser QK, charging` via resistance MA, cam Contact C23 and contact bd5, and also places tube FJ and relay J in parallel with condenser QJ by connecting relay J at lead I6 to minus lead I by contact 1x13 Via cam contacts C28 and lead I'I.

In position 6 the charging circuit for condenser QL is again completed via resistance RRA and cam contacts CI, andAits reset circuit via contacts rrl, cd2 and low resistance ZRA to prepare once more for determining the extent of the subsequent all-red signal period when right of way is transferred to the B approach. A complete cycle of operation of the controller has now been described.

Upon each operation of the solenoid S condensers QJ and QK are reset respectively by op eration of contacts S2 and S3 near the limit of the solenoid stroke, via small limiting Vresistances ZJ and ZK respectively, to assure that the condensers will be fully discharged and ready to commence their next timing actions following each operation of the solenoid to step the cam shaft from one position to the next. Condenser QL 75 which is charged cumulatively over'several periods at a time is discharged in initial green periods 2 and 5 by low resistances ZRA and ZRB respectively. Thefsame resistances serve to reset condenser QL upon A approach vehicle actuations in positions 6 and I and upon B approach vehicle actuations in positions 3 and 4 as previously explained. For example in position 2 condenser QL is discharged by a circuit from QL over lead 2 I, cam contacts C I, low resistance ZRA, lead 323, contacts cd2, Trl, and lead 22 tominus lead I.

The switches PB and PA are so-called arterial or recall switches and each when closed assures that right of way will be returned to its associated approach in the absence of traffic thereon. Their reiectfwith either one switch closed alone is to simulate the' action of the detectors when their respective approaches are not receiving right of way, byenergizing relay AD in Bright of way positions2 and A3 through switch PA or relay `BD in A right of waypositions 5 and 6 through switch PB. These switches therefore produce no prolonging of right of way periods. With both vswitches closed the controllerwill operate to accord right of way cyclically for minimum periods extendable by traffic actuation. If the setting of `resistance RRA is for a period in excess of the sum of vehicle and amber intervals VAV and LA, and that of resistance RRB for a period in excess ofthe sum of the periodsproduced by VB and LB, all-redlperiods equal to their excess differences will be interposed in the cycle when no traiic' is passing. Y v v InA some installations it vmay be desired to provide an overall clearance interval for travel from only vone direction of approach and in such instance oneof the switches ARS or vBRS is opened corresponding to the phase onwhich it is desired to omit the assured overall clearance and all-red period. If for example the overall clearanceperiod for the A approach is omitted switch ARS is opened. This renders relay RR incapable of operation in position I at the end the A approach amber interval, the al1-red signal display in position 2 is thus eliminated and the approach B initial green signals are displayed and timed immediately in position 2. The all-red intervaly following approach B amber would in this instance be interposed as usual since switch BRS is assumed to remain closed. For ordinary operation at a restricted zone or bridge BR however both switches ARS and BRS would be closed as shown. f

In certain instances when one of switches ARS orBRS is openedv the arterial or reverting switch 4for the opposing approach may be closed thus ensuring that inthe absence of traic right of way will always be returned to one approach and that an assured overall clearance period will be accorded to traflic entering the restricted area on such approach, and that following transfer of right of way to the opposite approach the right of way will subsequently be automatically retransferredto the first approach.

summarizing it will be appreciated from the the said vehicle. vIf the full vperiodtimed 'by condenser QL-is completed prior to actuation on the second approach, right of way will be laccorded to the second approachimmediatelyupon actuation thereon followingthe usual brief' amber period. If, however,the fulll period ofl condenser QL has not been so completed whensuchactuation on thesecond approach occ`urs, condenser QL willnot be charged suliicientlyr-to discharge through relay J via contact 1'18 and therefore an all-red interval is introduced following the amber period until-the overall clearance period is completed by the charging of-condenser QL to the flash potential of tube FJ.

During the all red period the red signal isI maintained displayed to the second approach to prevent vehicles thereon'from proceeding into the area, and red is also shown to the first approach to prevent any vehicles subsequently approaching on the rst vapproach from entering the restricted area. The all red interval, terminated as soon as condenser QL ldischarges through tube FJ and relay J, isthus of suflicient duration for the last vehicle entering the area from the rst approach to complete its passage through thelarea,` and the actuating vehicleon the second approach will be delayedonly so long as any vehicle, travelling at average speed, remains in the restrictedarea.

It will be further appreciated that by opening either of switches ARS or BRS the overallclearance period following the right of way period on the phase corresponding may be eliminated. This type of operation is desirable when the'controller is installed for instance at the intersection of a very wide divided highway with a crossroad where a long clearance period is required'only on'the crossroad for vehicles to clear the long crossing of the wide highway. v

In the embodiment ofthe system as previously described herein it will be noted that an amber signal is displayed'for a short periodfollowing the green signal period and before the red signal period on each lane, which is a very widely -used sequence of signal colors. It will be understood, however, that other suitable sequences of signal colors may be used with minor rearrangements of the signal connections or cams. For example, if it is desired to havela direct change from green to red and to omit the amber signal as is the practice in sorneV localities this can be accomplished by changing the position of switchesfSWA and SWB appearing in Fig.` 1. As shown in-Fig. l these switches are inpositiontoprovide the amber signal as previously described, and for this purpose switch SWAfco'nnects lead '35`to lead 33 and the vA amber signal whereas switch SWB connectslead to lead 3l and the B amber signal. Y

If it is desired to omit the 'ambersignal an to have the red signal come on at the beginning of 'what would be thefamber signal period'then switch SWA is shifted to'connect lead235- to lead 3d and the A red signalRA andswitchSWBis shifted to'connect lead 32 to leadf30 and the B red signal RB, and the ambersignalsAB'and'AA can be omitted. 'It will be observed from the cam position chart that this shift ini the positionv of switches SvVAand SWB will causethedisplay of signal RA in position l as well as in-'position`2, 3 and ll, for 'eXample,-and-'will causefsignaLRB to be displayed inpositionl as Well as 5,f6and` I.

In some localitiesi't is the' practiceto=have -a dark period with -no signalsldisplayedfonf-aftraic lane vfollowing thegreen 'signal r`vperiod5 Aon1 that lane-:and before'the red signal period on that lane and -while'the red signal is maintainedon vthe opposite lane. sequence of this type can be provided by omission v'of theambersignals AA and VAB with the switches It will be noted that a SWA and SWB in the positions shown in Fig. 1, 'and with this arrangement'tlre'signals will be ydarkonfapproach Ain cam shaft position l and on approach'B in camshaft position 4.

It -will beunderstood by those skilled in the art thatother changes inthe design or construction of the disclosed embodiment of the invention,

vsuch-asforexample the substitution of mechani- Vcal timers or other electronic timers for the par'- way signal controller for according right of way `alternately'to the lanes respectively in response to-traffic'arriving in the respective lanes and to interrupt right of way in the other lane when right of way is accorded to one lane, means forming la partfof said controller to interrupt right of Way in'both lanes after termination of accord of right of way in one lane and'before accord 'of right of way to the other lane in response to traflic arriving intlielatterlane, and means for timing suchinterruption of right of way to both lanes to provide an ultimate length of time sufiicient' to permit a unit oftraffic to clear through the zone of interference `butto reduce the time of interruption of right of way to both lanes from such ultimate length in accordance with the amount of time the right of way may have remained on the one lane after arrival of the last prior-vehicle there and before arrival of the first lvehicle on the other lane while right of way is interrupted in the latter lane.

2. A trac control system for interfering traffic lanes in which the Zone of interference lbetween the lanes is relatively long, including a 'right of way signal controller for according right fof wayalternately to the lanes respectively in respense' to traiiic arriving in the respective lanes and to' interrupt right of way in the other Vlane when right of way is accorded to one lane, means forming a party of said controller to interrupt 'right of way in both-lanes after termination of laccordfof right of way in one lane and before accord of right of way to the other lane in response to traffic arriving in the latter lane, and means for timing-such Vinterruption of right of way to `both lanes-'to provide an ultimate length of time sufcient to permit a unit of traffic to clear throughlthe zone of interference but to reduce thev time -ofv interruption" of right of Way to both flanes'rom such ultimate length in accordance lwithE theamount of time which may have Velapsed from' the arrival of thelast vehicle having right of way on one lane before the arrival of the rst vehicle on the other lane while right of way is interrupted `in 'the' latter lane.

'-3. 'A'traflc control system for the accord of right of way alternately to two approaches to a relatively long zone of interference, including means according right of `wayI to either one approach responsive to traffic arrivingV therein and transferring right of way to the. other approach xin response to traflic "in the 'latter approach,

means providing a short period of extension of right of -way following the arrival of each of a series of vehicles ron one approach while right of way :is accorded-thereto, means Vproviding an overall clearance time period following the arrival Aof each such'vehicle on said oneapproach withsuch overall clearance time vvperiod of considerably greater length than the right of way extension period, and Ymeans to interrupt right of way in the first approach while maintaining interruption of right of way in the second approach in response to the arrival of the iirst vehicle on said second approach `upon termination of said right of way extensionrperiod on the first approach, and means Adetermining the time length of such interruption of right of way -to both approaches in accordance with V the Idiierence between the overall clearance ,time and the right of way extension time.

4. A traic lcontrol system fortwo approaches to a -relatively long zone of traffic interierenca including a signal controller to accord right of way alternately to the two vapproaches 'responsive to traiiic in the respective approaches, means forming a part of said controller to time each such accord of right of way and to 4provide a short period of extension of s uch right of way on either one approach following the arrival of a vehicle on said one approach while right :of way is accorded to said one approach, and :means providing an overall clearance time period Vfollowing the arrival of such vehicle with such clearance Vtime period of considerably greater length than the right or" way extension time period, means to interrupt right of way thesaid one approach while maintaining interruption of right of way in the second approach. at completion of such extension period in response to the arrival of the first vehicle on the second approach while right of way is interrupted therein, and means controlling the lastnamed means to determine the time length ofisuch interruption of right of way to 'both approaches .in accordance with the difference between the overall clearance time period and ithe rightof way eX- tension time period.

5. A traiilc control :system fortwo approaches to a relatively long Zone of traflic interference, including a right of way controller for accord of right of way alternately to the respective approaches in response to traffic on the respective approaches, a timer for controlling the time of such accord of right of way and having a relatively short time period for prolongation of right of way from the arrival of each vehicle arriving in one approach while right of way is accorded thereto and at the end of such time period to interrupt right of .way on said one approach in response to traiiic arriving on the second approach, a second timer to time a longer time period than the rst mentioned period from the arrival of each vehicle having the right of way on said one approach and of sulcient time length to permit such arrivingvehicles to clear through the entire zone of interference, and means controlled by said second timer to delay accord of right of way to said second approach in response to arrival of the iirst vehicle in said second approach so that a period of interruption of right of way to Tooth lanes will ensue between termination of the time period of the first timer and termination of the time period of the second timer but only of sufiicient length to clear the last vehicle arriving with the right .of way onsaid one approach.

6. Atraiiic control system for interieringtraffic lanes in which there is a relatively long zone lane while such go signalis so operated, means responsive toa -vehiclearriving on the-other lane and yto termination of said short timeperiod to operate said mechanism to its other position, andoperate the stop'signal onsaid first lane, and further timing-means timing a `further-time period longer than saidV short time period fromithe arrival of teach oi said series of vehicles onvsaid one lane lto maintain operation-ofthe stop'signal in the second lane and to delay operation ,of the go signal in said second lane in the said other position of said signalmechanism for a suicient time to Ipermit the 'last vehicle arriving on said one lane to clear :the zone of interference.

'1. vA -trairlc control-system for interfering :trafc Alanes in which there is aA relatively long zone of interference Ybetween such lanes, including green, yellow and red trailic signals for the -respective lanes, traic signal control mechanism for displaying said green signal to one of the lanes at a time and the redsignal concurrently to the other lane, and Vfor'displaying the yellow signal after the green signal and before the red signal, timing means for controlling the .time of Y display of the green signal Vfora minimum period andfor yprolonging said y'display period for a short period following each -of -a Yseries of vehicles arriving in said one lane,V means responsive to arrival of la vehicle in the second lane while the green` signal -is displayed in the `irst lane to operatefsaid signalmechanism to'terminate display of the green signal Ain said-nrst lane and to initiate display of the yellow signaltherein vupon termination ofthe lastof-saidshort periods .of prolongation, timing means to terminaterthe display of the yellow signal after 'a brief period and thereupon Vto display the red signal in said one lane, and further timing means to time a period following eachof said Aseries of vehicles arriving in said first lane and extending over said yellow period and to Ymaintain the red 'signal displayed i-n said second lane lwhile 4the red signal is-also displayed in said first lane for a suiicient time after the end of said yellow period to permit the last of ,said series of vehicles on said rst lane to clearthrough the Zone of interference, and thereupon to 'terminate the display of red signal in said second lane and substitute fthe display of the'greensignal therein.

V8. A traic control system fortwo approaches to a relativelylong Zone of -traiic interference, including signalling means for according and interrupting fright oi' way to the respective approaches, tralic actuated means in the respective approaches to be actuated by traffic proceeding toward the said signalling means and said zone of interference, signal operating mechanism connected to said signalling means and said trafc actuated means for operating said signalling means lto accord right of Vwayto one approach and interrupt right of way vto the .other approach in responserto tramo actuation vvin the Aiirst approach, means forming a part of said mechanism to maintain right of way in said rst approach for a short time extension period following each of a series of actuations of the traffic actuated means in said rst approach by several units of traiilc, timing means for timing a longer time period following each of such series of traflic actuations, means for terminating accord of right of way to said rst approach by such signalling means upon expiration of said short time period and responsive to traffic actuation in the second approach, and means for interrupting right of way in said first approach by said signals followf ing termination of right of way and for maintaining interruption of right of way in said second approach until completion of said longer time period before according right of way to said second approach responsive to actuations therein, whereby accord of right of way to said second approach will be delayed after interruption of right of way to said first approach for sufficient time only to clear the last unit of traffic enter-f ing the zone of interference from said rst approach.

9. In -a traffic signal control system for two mutually interfering trairic lanes, signalling means for according and interrupting right of way on the lanes, traffic actuatable means in the lanes, control means connected to the signaling means and to the traffic actuatable means and responsive to actuation of the traffic actuated means in one of the lanes to cause the signalling means to interrupt right of way on the other lane and to accord right of way to said one lane for at least a predetermined minimum period, means responsive to actuation of the traflic actuated means on said other lane to cause the signalling means to interrupt right of way on said one lane and to accord right of way to said other lane after expiration of the minimum right of way period on said one lane, timer means for timing an overall clearance period of sufficient length for a unit of traffic on said one lane to clear the other interfering lane and connected to have its timing initiated by actuation of the traic actuated means on said one lane during the right of Way period thereon, and means for causing the signalling means to maintain interruption of right of way on said opposing lane -and to delay according of right of way to said opposing lane after completion of said minimum right of way period and after actuation of the traino actuated means in said opposing lane until the clearance period of said timer means has been completed.

10. In a traiiic signal control system for two mutually interfering traffic lanes, sign-alling means for according and interrupting right of way on the lanes, trailic actuatable means in the lanes, control means connected to the signalling means and to the trame actuatable means and responsive to actuation of the trafc actuated means in one of the lanes to cause the signalling means to interrupt right of way on the other lane and to accord right of way to said one lane for at least a predetermined minimum period, means responsive to actuation of the trafc actuated means on said other lane to cause the signalling means to interrupt right of way on said one lane and to accord right of Way to said other lane after expiration of the minimum right of way period on said one lane, timer means for timing an overall clearance period of suicient length for a unit of traiTic on said one lane to clear the other interfering lane, means for initiating operation of said timer means by actuation of the traffic actuated means on said one lane during the right of way period thereon and for resetting operation of said timer means for restarting its timing period by further actuations within the right of way period thereon, and means for causing the signalling means to maintain interruption of right of way on said opposing lane and to delay according of right of way to said opposing lane after completion of said minimum right of way period and after actuation of the traiiic actuated means in said opposing lane until the clearance period of said timer means has been completed.

11. In a traiiic control system for two mutually interfering trailic lanes, 'signalling means for according and interrupting right of Way to the lanes, trafc actuatable means in the lanes, control means connected to said signalling means and traiic actuated means and responsive to actuation of the traic actuated means in one of the lanes to cause the signalling means to interrupt right of way on the opposing lane and to accord right of way to said one lane for at least the sum of the duration of -a fixed initial interval and a vehicle interval, means responsive to actuation of the traffic actuated means on said one lane during said vehicle interval to prolong accord of right of way for a further vehicle interval, means responsive to actuation of the traffic actuated means on said opposing lane while4 right of way is on said one lane to cause transfer of accord of right of way to said opposing lane at the end of said further vehicle interval, timer means for timing an overall clearance time period in which a unit of tramo on said one lane entering the interference area during the right of way period for said one lane may pass entirely through the area, means for initiating operation of said timer at the start of said vehicle interval, means responsive to traiiic actuation on said one lane within said vehicle interval to reset said timer to assure a full period for the actuating unit of traffic to clear the area, means for maintaining the interruption of right of way on said opposing lane after trafc actuation of the traffic actuated means therein and completion of said vehicle interval until the clearance period of said timer has been completed.

l2. In a traffic control system for mutually interfering traiic lanes having signalling means L for displaying accord andinterruption of right of way to the lanes, traffic actuated means in the approach of each of the lanes to the area of interference, control means connected to the traiic actuated means and to the signalling means and operable responsive to actuation of the traffic actuated means in one of the lanes to cause the signalling means to accord of right of way to only said one of the lanes for at least a minimum period, means responsive to actuation of the traiic actuated means in another lane to cause transfer of accord of right of Way to said another lane after the minimum period on said one lane, means operative while right of way is accorded on said one lane, in response to traffic actuation of the traflic actuated means on said one lane to time an overall clearance period in which the actuating unit of traino will be assured time to pass entirely through the interference area and means for preventing the signalling means from according right of way to said another lane in response to actuation of the traiiic actuated means therein until the timing means has completed its clearance time period.

13. In a trailic control system for two mutually interfering traffic lanes including signalling aaliaioo means for displaying accord and interruption of right of way to the lanes, traffic actuatable means in the approaches of the lanes to an area in which they are mutually interfering, control means connected to the signalling means and to the traiiic actuated means and responsive to actuation of the traic actuated means in one lane to cause the signalling means to accord right of way to said one lane and to interrupt right of way on the opposing lane for at least a predetermined minimum' period, and for a further extension period by further actuation during said minimum period, means including a timer initiated by actuation of the trame actuated means in said one lane while right of way is on said one lane to time an overall clearance period in which the unit of traic causing the actuation may pass entirely through the interference area, means responsive to actuation of the traffic actuated means in said opposing lane while right of way is on said one lane to cause the signalling means to interrupt right of way on said one lane after the minimum period while maintaining right of way interrupted on said opposing lane and to cause accord of right of way to said opposing lane only upon expiration of said clearance period, and means responsive to such actuation in said opposing lane to provide a maximum time limit to such further extension by such further actuation.

14. In a traffic controlled system for the accord of right of way alternately to two approaches to a relatively long Zone of traiic interference in response to traiiic on the respective approaches in which a series of short periods of extension of right of way are provided for a series of relatively closely spaced vehicles arriving on one approach while right of way is accorded thereto, and in which right of way is interrupted in said one approach upon termination of such extension period in response to the arrival of a vehicle on the other approach, means delaying accord of right of way to said second approach in response to said vehicles therein after such interruption of right of way in the rst approach, a timing device to control said last named means so as to terminate such interruption of right of way to both approaches upon completion of its time period, and means connecting said timing device to start a timing period from the arrival of each of said series of vehicles on said one approach, whereby accord of right of way to the second approach in response to a vehicle therein will be delayed following the last vehicle to arrive on the rst approach for a sufficient time to clear said last vehicle through the zone of interference.

15. In a trafc control system for accord of right of way alternately to two approaches to a relatively long zone of interference responsive to trafc in the respective approaches, timing means actuated by traiiic to time a short period following traic actuation on one approach while right of way is accorded thereto and to terminate accord of right of way thereto at the end of such period responsive only to traiiic in the opposite approach, and a second timing means actuatedV by trafc for timing a longer period following such actuation in said one approach having the right of way to maintain interruption of right of way in both approaches for a sufficient time period following suchy termination ofY right of way in said rst approach t'o permit the last unit of tramo from said first approach to clear through the entire Zone of interference.

16. A Vvehicle trafilc control system for two interfering traiiic lanes in which there is a relatively long zone of interference between said lanes, including go and stop traiiic signal circuits for the respective lanes, signal circuit switching mechanism having alternate control positions for said circuits includingV one position for normally energizing the go signal for one line and the stop signal for the second lane and a second position for normally energizing the go signal for the second lane and the stopfsignal for the first lane, traflc actuatable relay means individual to the respective lanes, a resettable time switch having a short timing period, electrical operating means controlled by said time switch and by the traffic actuated relay of the second lane in such one position to operate said mechanism to its second position at completion of said short timing period responsive to actuation of said relay, a second resettable time switch having a considerably longer timing period than the rst time switch, control circuits for said time switches connected with said mechanism and said tralc actuatable relay means to reset both of said time switches to restart their timing responsive to each traflic actuation on said first lane in the rst position of said mechanism, relay means interposed between said mechanism and said signal circuits and connected to said-mecha- Y nism to be operated by operation of said mechanism from said first position to said second position to interrupt the normal energization of the go signal and to energize the stop signal for the second lane in the second position when so operated, and a control circuit for the last named relay means controlled by said second time switch to maintain said last named relay means kso operated until completion of timing by said second time switch and thereupon to release the relay means to restore the normal energization of the signals in said second position, whereby the last vehicle arriving on said one lane will :be provided time to clear the zone of interference before energization of the go signal for the second lane.

HARRY A. WILCOX. JOI-IN L. BARKER.

CERTFICATE 0F CORRECTION. Patent 1&0." 2,219,100. July. 15, 19in.

- HARRY A. wILcox, ET AL.

It is hereby certified that error appears in the printed specification. of the above numbered patent requiring correction as follows: Page 5, first column, line 1.1.8, after position l'' and before the period insert --by a ratcheting arrangement (not sshown);v page Y, second column, line 3.0., for "lead 525" read --ieae 23"; and that the Said Letters patent .should be read with this correction thereinthat -the same may conform` to the recordA of the 'case lin the Patent Office.

signed and, sealed` this 28th day of April, A. D. 19m.

l Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

